Comparison of different methods for diagnosis of porcine proliferative enteropathy

The objectives of this study were: (1) to compare 2 methods of serology; (2) to compare 3 histologic techniques; and (3) to compare 2 methods of detecting shedding in pigs experimentally challenged with Lawsonia intracellularis. The sensitivities of these tests were determined by the detection of infection. Forty 5-week-old pigs were inoculated on day 0 with intestinal homogenate from pigs with proliferative enteropathy (PE). Clinical evaluation was done on day 7 and daily from day 14 to 28 postinoculation. Fecal shedding of L. intracellularis was monitored by use of polymerase chain reaction (PCR) analysis and immunoperoxidase staining at 7-day intervals. Serum was obtained on days 0 and 28 for serologic testing by glass slide and tissue culture indirect fluorescent antibody tests. At euthanasia on day 28, gross intestinal lesions were evaluated and ileum samples collected for histologic analyses. Ileal histologic sections from each animal were stained by hematoxylin and eosin, Warthin-Starry silver stain, and immunohistochemistry (IHC). Of the 40 pigs, 36 had gross lesions typical of PE at necropsy. The percentage of agreement between the 2 serologic methods was 94.4%. Immunoperoxidase stain of fecal smears was more sensitive than PCR for detecting fecal shedding, especially on day 21 (89.5% and 60.5%, respectively) and day 28 (59.4% and 37.5%, respectively) post-inoculation. The IHC stain was much more sensitive for detecting infection than the routinely used hematoxylin and eosin and Warthin-Starry silver stains. In conclusion, in experimentally infected pigs, both serologic methods were appropriate techniques for detecting infection. For fecal samples, PCR has low sensitivity. Immunohistochemistry is the best diagnostic tool for formalin-fixed samples.     

Comparison of 2 serologic tests for the diagnosis of porcine proliferative enteropathy

The purpose of this study was to compare results from 2 serological assays at the individual- and herd-level for porcine proliferative enteropathy diagnosis. Cohen’s kappa coefficient (k) was used to measure agreement. The tests tend to show better agreement when used at the herd level.     

Evaluation of a novel enzyme-linked immunosorbent assay for serological diagnosis of porcine proliferative enteropathy

A specific enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to the porcine pathogen Lawsonia intracellularis was developed and evaluated using sera from na?ve, naturally infected as well as experimentally infected pigs. On the basis of 37 serum samples collected from experimentally infected pigs and 62 serum samples from naturally infected pigs the sensitivity of the ELISA was calculated to 98.0%. The specificity of the test was 99.3%, calculated on the basis of 273 serum samples collected in six herds free of L. intracellularis after medicated eradication. The novel ELISA was a specific and sensitive method for detecting specific antibodies, and may be a good alternative to the existing serological tests for L. intracellularis. It may be usable for diagnosis of proliferative enteropathy and for determination of a herd's epidemiologic status.     

广西猪增生性肠炎的PCR诊断

猪增生性肠炎(porcine proliferative enteropathy,PPE),又称猪回肠炎,是由胞内劳森氏菌(Lawsonia intracellularis,LI)引起的接触性传染病[1].1931年首次报道,目前已经呈全球性流行,亚洲地区如台湾、日本、韩国等近年来也发现猪增生性肠炎;     

Development and validation of an enzyme-linked immunosorbent assay for the diagnosis of porcine proliferative enteropathy.

The objective of this study was to develop an indirect enzyme-linked immunosorbent assay (ELISA) using a sonicated pure culture of Lawsonia intracellularis as the antigen (So-ELISA). A total of 332 serum samples, consisting of 232 experimentally infected animals and 100 animals naturally infected with L. intracellularis, were used to assess the diagnostic sensitivity. Three hundred and fifty-five sera from uninfected animals were used to determine the diagnostic specificity. The receiver operating characteristic and mean +3 standard deviation of optical density (OD) values from uninfected animals were used for selecting cut-off points. The diagnostic accuracy of So-ELISA was considered to be high as the area under the curve index was 0.991 with 0.0029 standard error. The optimal cut-off for So-ELISA was set at 0.45 OD with 89.8% sensitivity and 99.4% specificity based on a combination of good sensitivity and high specificity. No cross-reactivity was found in sera from pigs exposed to Brachyspira pilosicoli, B. hyodysenteriae, Campylobacter mucosalis, C. jejuni, or C. coli. Inter- and intracoefficient of variation of all control sera tested with So-ELISA was less than 10%. The observed agreements between So-ELISA and the immunoperoxidase monolayer assay tested with experimental challenge animals and field samples were 95.08% with 0.88 kappa and 90.65% with 0.74 kappa value, respectively. So-ELISA was able to detect the seroconversion of infected animals at 2 to 4 weeks after exposure to L. intracellularis. Based on the validation results, So-ELISA could be used as an alternative serology for proliferative enteropathy diagnosis.     

Identifying obstacles to reducing the use of antibiotics to control porcine proliferative enteropathy

Proliferative enteropathy (PE) is an enteric disease of pigs that results in diarrhoea, reduced growth rate, reduced feed conversion efficiency and sometimes death. A survey of 13 pig veterinary practitioners in Australia was conducted to determine: (1) PE control strategies (antibiotics and vaccination), (2) how the efficacies of these strategies are evaluated and (3) how reliance on antibiotics could be reduced by increasing vaccine adoption. Antibiotics were routinely prescribed in the diets of weaner, grower and finisher pigs by 9/13, 10/13 and 8/13 veterinarians, respectively, if vaccination was not implemented. Water-soluble antibiotics were prescribed less frequently than in-feed antibiotics. Efficacy of control strategies was assessed most often through reduced clinical signs (diarrhoea, 'tail-ender' pigs, death) and reduced lesion incidence at abattoir postmortem inspection. Twelve practitioners had recommended PE vaccination to their clients in the previous 6 months. Barriers to continued vaccine implementation included perceived lack of efficacy for pigs housed in bedded systems, high cost relative to medication and difficulties in vaccinating pigs post-weaning.     

Surveillance for porcine proliferative enteropathy in Alberta by using routine diagnostic laboratory data

Data from the Food Safety Division, Alberta Agriculture, Food and Rural Development were analyzed to determine the frequency of diagnosis of porcine proliferative enteropathy (PPE) relative to the diagnosis of other porcine enteric infections between 1993 and 1997. Next to colibacillosis, PPE was the most commonly diagnosed enteric disease among those reported.     

Equine proliferative enteropathy – a review of recent developments

Equine proliferative enteropathy (EPE) is a disease of foals caused by the obligate intracellular organism Lawsonia intracellularis. This emerging disease affects mainly weanling foals and causes fever, lethargy, peripheral oedema, diarrhoea, colic and weight loss. The diagnosis of EPE may be challenging and relies on the presence of hypoproteinaemia, thickening of segments of the small intestinal wall observed upon abdominal ultrasonography, positive serology and molecular detection of L. intracellularis in faeces. Although the clinical entity, diagnostic approach and treatment of EPE are well established and described, the epidemiology for this disease has remained largely unaddressed. This article focuses on new developments in the field of EPE, including epidemiology, pathophysiology, clinical signs, diagnosis, treatment and prevention. The Summary is available in Chinese – see Supporting information.     

A comparative study of an indirect fluorescent antibody test and an immunoperoxidase monolayer assay for the diagnosis of porcine proliferative enteropathy.

The currently used indirect fluorescent antibody test (IFAT) for the detection of antibodies against porcine proliferative enteropathy (PPE) was compared to an immunoperoxidase monolayer assay (IPMA). Serum samples used in this comparison were collected from 5-week-old pigs on day 0 (pre-experimental challenge) and on days 7, 14, 21, and 28 after oral inoculation with intestinal homogenate from pigs affected by PPE (28 challenged pigs) and sucrose phosphate glutamate solution (2 control pigs). All animals were euthanized 4 weeks after inoculation. Immunohistochemistry staining was applied to formalin-fixed, paraffin-embedded sections of ileum for the detection of Lawsonia intracellularis antigen. The serology results with each method agreed in all samples, except on days 0 and 7 in 1 control animal, which was positive by IPMA, but negative by IFAT. The percentage of agreement between IFAT and IPMA was 98.6%.     

Validation of an immunoperoxidase monolayer assay as a serologic test for porcine proliferative enteropathy.

The sensitivity and specificity of an immunoperoxidase monolayer assay (IPMA) was evaluated in a blind serologic study of a group of disease-free pigs and a group of pigs experimentally infected with intestinal homogenate containing Lawsonia intracellularis organisms. Sixty pigs from the control group were kept in the source farm, and another 60 animals were transferred to an isolation unit aid challenged intragastrically. All animals were bled before and 21 days after challenge. Fecal samples were collected on the same dates. The IPMA results were tested for sensitivity and specificity in a 2 x 2 table using the challenged and nonchallenged status as gold standard. Sensitivity and specificity were evaluated for different cutoff points (serum dilutions). Specificities of 100% were obtained for all the serum dilutions tested (1:15, 1:30, 1:60, and 1:120). The sensitivity levels were 90.7%, 88.9%, 81.5%, and 75.9% for the serum dilutions 1:15, 1:30, 1:60, and 1:120, respectively. The sensitivity of the dilution 1:15 was slightly, but not significantly, higher than the dilution currently used as the cutoff point (1:30). Cross-reactivity of the IPMA test was evaluated using sera from pigs experimentally inoculated with Brachyspira pilosicoli and various Campylobacter species. All these samples were negative. Sera samples from 3 porcine proliferative enteropathy known negative populations, 40 growing pigs from 2 commercial farms and a group of 6 cesarean-derived and colostrum-deprived pigs, also tested negative by IPMA. The IPMA serologic test with the cutoff point of 1:30 showed specificity of 100% and sensitivity close to 90% and, therefore, is an appropriate diagnostic test for herd screening but not for diagnosing PPE on the individual level.     

Immunohistochemistry and polymerase chain reaction for the detection of Lawsonia intracellularis in porcine intestinal tissues with proliferative enteropathy

Detection method of Lawsonia intracellularis was studied in formalin-fixed paraffin-embedded intestinal tissues from 5 naturally infected pigs by immunohistochemistry with a monoclonal antibody against outer membrane protein of L. intracellularis. Warthin-Starry silver stain revealed clusters of argyrophilic, slightly curved rod-shaped organisms in the apical cytoplasm of enterocytes. Immunohistochemical staining with a L. intracellularis-specific monoclonal antibody confirmed the presence of the organism in the apical cytoplasm of hyperplastic enterocytes. The presence of L. intracellularis in the ileum of pig with proliferative enteropathy was confirmed by polymerase chain reaction (PCR) further on the basis of amplification of 319 base pair products specific for porcine L. intracellularis chromosomal DNA. Immunohistochemistry and PCR may be a complementary method to confirm the diagnosis of L. intracellularis infection in pigs.     

胞内劳森菌及其所致的增殖性肠病

本综述介绍的胞内劳森菌 ,是一种弯曲状杆菌 ,无鞭毛 ,抗酸染色阳性 ,能为Warthin Starry或Lavaditti镀银法着色。该菌存在于病畜肠细胞原生质内 ,至今不能人工培养 ,但可在一些肠细胞培养中生长 ,引起猪增殖性肠病 ,还见于仓鼠、马、鹿、雪貂、大鼠、兔、狐、鸵鸟、鸸鹋等动物。可用病理学、血清学、细菌学、PCR等方法诊断 ,防治可用抗生素 ,如金霉素、tylosin、dimetridiazole、carbadax、timulin等治疗 ,至今无疫苗。     

Reduced use of antimicrobials after vaccination of pigs against porcine proliferative enteropathy in a Danish SPF herd

The present study explored whether the use of group medication with antibiotics in a Danish pig herd was reduced after vaccination of the pigs against proliferative enteropathy (PE) caused by Lawsonia intracellularis. 7900 pigs originating from a single commercial sow herd were vaccinated against L. intracellularis, whereas 7756 pigs were kept as non-vaccinated controls. The pigs were included batch-wise in the study with every second batch being vaccinated. In the vaccinated batches, the consumption of oxytetracykline to treat PE was reduced by 79%, with a significantly lower number of pigs being treated (P < 0.0001). Vaccination also resulted in a highly significant improvement of average daily weight gain (+ 46 g/day; P = 9.55 × 10^-31) and carcase weight (+ 1.25 kg; P = 4.54 × 10^-05) as well as a shortened fattening period (-8 days; P = 2.01 × 10^-45).     

Lawsonia intracellularis proliferative enteropathy in a filly

Proliferative enteropathy (PE) caused by the obligate intracellular bacterium Lawsonia intracellularis is a disease of high economic impact in swine worldwide. In most other species the disease occurs as a sporadic infection. This paper reports a PE caused by L. intracellularis in a 9-month-old Pura Raza Espa?ola filly with a history of profuse diarrhoea. Pathological lesions consisted of a severe proliferative enteritis associated with argyrophilic bacteria in the apical cytoplasm of proliferating crypt epithelium. Characteristic PCR products confirmed the presumptive diagnosis of L. intracellularis infection. To our knowledge this is the first report of PE in a horse in Europe caused by L. intracellularis.     

Equine proliferative enteropathy caused by Lawsonia intracellularis

Equine proliferative enteropathy (EPE) is a disease of foals caused by the obligate intracellular organism Lawsonia intracellularis. This emerging disease affects mainly weanling foals and causes fever, lethargy, peripheral oedema, diarrhoea, colic and weight loss. The diagnosis of EPE may be challenging and relies on the presence of hypoproteinaemia, thickening of segments of the small intestinal wall observed on abdominal ultrasonography, positive serology and molecular detection of L. intracellularis in faeces. Although the clinical entity, diagnostic work-up and treatment of EPE are well established and described, the epidemiology for this disease has remained largely unaddressed. This article reviews the aetiology, epidemiology, clinical signs, diagnosis, treatment and prevention of EPE.